1. Field of the Invention
The invention relates to a method of imaging a portion of a body placed in a static magnetic field by means of magnetic resonance (MR), which method includes measurement of ECG data of the body, determining an acquisition period from the ECG data in order to synchronize measurement of MR signals to a cyclic movement of the body, generating an MR sequence during the acquisition period of RF fields and magnetic gradient fields, and reconstructing an image of the portion of the body from the MR signals. The invention further relates to an MR apparatus for carrying out such a method and to an ECG device suitable for use in an MR apparatus.
2. Description of Related Arts
Such a method and apparatus are known from U.S. Pat. No. 5,526,813.
As is well known a k-space is understood to be a spatial frequency domain in which an MR signal is measured along a trajectory and the measured values yield the inverse Fourier transformed values of the image of the body. The trajectory in the k-space is determined by the time integral of temporary gradient fields over a time interval from the excitation of the nuclear spins to the actual instant of measurement of the MR signal. Furthermore, gradients are understood as being temporary magnetic fields which are superposed on the steady magnetic field and cause a gradient of the static magnetic field in three respective orthogonal directions. Generally speaking in a 2-D imaging sequence, the gradient in a first direction is denoted as a read gradient, the gradient in a second direction as a phase-encoding gradient and the gradient in a third direction as a slice-encoding gradient.
In the known method the quality of MR images is improved by the synchronization of the acquisition of MR signals with a heart beat of the body. Hereto the acquisition period of the MR signals is determined from the measured ECG data, for example, from the R-wave. In order to reduce erroneous determination of the acquisition periods the ECG data is filtered. By the filtering, noise is reduced from the ECG data obtained from the body. An MR image of the region of the body is then reconstructed from a set of MR signals from the portion of the body measured during consecutive synchronized acquisition periods. A drawback of the known method is that the filtering of the ECG data may be unreliable and as a result erroneous acquisition periods may be determined from the filtered ECG data.